Y axis problem

Hi after many successful hours of printing suddenly my Y axis will not zero. It gets to about 2 inches from the contact switch and the stepper motor pauses and hitches and then continues and then stops and then finally gets to the stop.

The first symptom occurred mid print when suddenly the printing in the y axis was way off. (like 75mm or so)

Is this the:

Motor
Harness
System board

I checked the belt and it seems fine. Tension is good and I can’t find any missing teeth.

How do I troubleshoot this?

The small setscrew on the Y motor belt pulley is likely loose. The tension looks correct in that scenario, but the bed can still slip. It’s that or a loose motor wire. Or maybe a broken motor shaft but thats very rare.

Well the set screws are tight.

Here’s another thing I’ve noticed, when it gets to the area near where it jams, the stepper motor is still making a sound like it is turning, but the shaft and pulley are not turning. How is the shaft held inside the stepper? Is it also a set screw? I am wondering if that is where the slipping is happening…

The shaft inside the stepper is held by the magnetic field :smiley: There is no screw inside, you can have a look here.

Are you able to move the bed without resistence all the way up and down?

The shaft is integral to the motor core. It’s glued in but good. If it’s twitching and not moving, that generally indicates half the motor wires are reversed and in magnetic oposition to the other half of the magnet in the motor. That would be wierd to just start occuring though. Usually you have to have one set of motor pins reversed for that to occur. Unless you swapped out a motor recently or had a pin fall out of the housing, thats unlikely. Only other thing I can think of is debris on the bed preventing movement. Try unscrewing the Y bed anchor mount from the bed and run it back and forth and see if it still jams.

Yes the bed moves well. I mean there is resistance but it’s from driving the belt and the stepper. It is constant and smooth.

Well the thing is the motor seems to operate fine and then stops as it approaches the relay stop. And then it seems to continue running, but the bed stops moving. After a few seconds it moves again and hits the stop. But while I can hear the stepper running, the bed is not moving and the shaft and pulley are stationary. It’s like the motor is stalling. But the bed moves freely by hand.

How did you check the set screw holding the pulley on? Did you take the correct size allen wrench and try to tighten?
You could have a wiring harness or plug problem, when it gets that far over the plug in the motor moves a bit or a wire connection has moved and it just takes one wire open out of the four to make the motor work as you described.

Yes I tightened the set screws (they were already very tight) but the problem remained.

I will remake the harnesses I have the proper molex connectors on hand anyway, so that’s a little luck. Hopefully it’s that simple. Thanks.

Your going to do too much work, just as the motor is running or starting to move wiggle the plug or wiring a bit and see what happens? Could be something simple… I hope!

Your going to do too much work, just as the motor is running or starting to move wiggle the plug or wiring a bit and see what happens? Could be something simple… I hope!

It was a broken shaft! I had ordered a new stepper because the connectors were fine. Just got the new one tonight and replaced the old stepper. When I took the pulley off, I noticed the shaft on the old stepper had some up/down play. So I pulled on it and the top portion of the shaft pulled right out! It broke about 9mm below the bottom edge of the milled flat.

It’s crazy that it was able to work at all!

Can this be repaired? Or is it not worth the effort?

Anyway my Taz is back up and running, printing away as we speak. Thanks for all the suggestions.

Not reparable, and motors are cheap enough its probably not worth the effort.

I figured as much. Anyway I cut the connector off for future use and dumped the rest. A shame it can’t be fixed easily the motor is fine.

ps I believe the printed stepper mount should be altered on the Y-axis. As it is now on the Taz 5, the pulley sits pretty high on the stepper shaft to be even with the belt. I would think raising up the stepper such that the drive pulley sits on the bottom of the stepper shaft would reduce the stress a lot in that shaft, and allow for higher accelerations and speeds without failure of the shaft.

I will work on a design and post it when I am finished.

Another option is to use a 605zz bearing on the far end of the stepper shaft, and build a bracket for it. Something like this one, but set up to fit a TAZ http://www.thingiverse.com/thing:249121

Here’s my revised stepper mount:

http://www.thingiverse.com/thing:1178068